A number of medical ailments are treated or treatable through the application of electrical stimulation to an afflicted portion of a human subject's body. Examples of electrical stimulation may include magnetic or inductive stimulation, which may make use of a changing magnetic field, and electric or capacitive stimulation in which an electric field may be applied to the tissue. Neurons, muscle, and tissue cells are forms of biological circuitry capable of carrying electrical signals and responding to electrical stimuli. For example, when an electrical conductor is passed through a magnetic field, an electric field is induced causing current to flow in the conductor. Because various parts of the body may act as a conductor, when a changing magnetic field is applied to the portion of the body, an electric field is created causing current to flow. In the context of biological tissue, for example, the resultant flow of electric current stimulates the tissue by causing neurons in the tissue to depolarize. Also, in the context of muscles, for example, muscles associated with the stimulated neurons contract. In essence, the flow of electrical current allows the body to stimulate typical and often desired chemical reactions.
Electrical stimulation has many beneficial and therapeutic biological effects. For example, the use of magnetic stimulation is effective in rehabilitating injured or paralyzed muscle groups. Another area in which magnetic stimulation is proving effective is treatment of the spine. The spinal cord is difficult to access directly because vertebrae surround it. Magnetic stimulation may be used to block the transmission of pain via nerves in the back (e.g., those responsible for lower back pain). Further, unlike the other medical procedures that stimulate the body, electrical stimulation may be non-invasive. For example, using magnetic fields to generate current in the body produces stimulation by passing the magnetic field through the skin of a human subject.
Magnetic stimulation also has proven effective in stimulating regions of the brain, which is composed predominantly of neurological tissue. One area of particular therapeutic interest is the treatment of neuropsychiatric disorders. It is believed that more than 28 million people in the United States alone suffer from some type of neuropsychiatric disorder. These include specific conditions such as depression, schizophrenia, mania, obsessive-compulsive disorder, panic disorders, just to name a few. One particular condition, depression, is the often referred to as the “common cold” of psychiatric disorders, believed to affect 19 million people in the United States alone, and possibly 340 million people worldwide. Modern medicine offers depression human subjects a number of treatment options, including several classes of anti-depressant medications like selective serotonin reuptake inhibitors (SSRI), MAIs, tricyclics, lithium, and electroconvulsive therapy (ECT). Yet many human subjects remain without satisfactory relief from the symptoms of depression.
Repetitive transcranial magnetic stimulation (rTMS) has been shown to have anti-depressant effects for human subjects, even those that do not respond to the traditional methods and medications. For example, a subconvulsive stimulation may be applied to the prefrontal cortex in a repetitive manner, causing a depolarization of cortical neuron membranes. The membranes are depolarized by the induction of small electric fields, usually in excess of 1 volt per centimeter (V/cm). These small electric fields result from a rapidly changing magnetic field applied non-invasively.
Therapeutic and diagnostic procedures, such as TMS for example, may require a technician to locate a treatment location (e.g., or target location that is used to determine the treatment location) before performing the therapeutic and/or diagnostic procedure. This process can be time consuming and burdensome. For example, the technician may be required to manually collect multiple points on a patient one-by-one to generate a model of the patient, and after the model is generated, locate the treatment location on the model.